To use linearly a power amplifier, a method of backing off the power amplifier or utilizing a linearizer is applied. However, the back-off method secures the linearity thereof, but has a problem that the output power and efficiency are decreased. Further, since the additional linearizer has a technical limit that it can support a bandwidth just up to a maximum of 100 MHz, the communication equipment such as a distributed antenna system for receiving a plurality of service bands requires the power amplifiers as many as the number of the service bands thereby causing an increase in power consumption, size, price and the like of communication devices.